1. Field of the Invention
This invention relates to mechanized center-pivot irrigation systems, having a corner system attached thereto to provide water to the corners of a field. More specifically, this invention relates to a system for path following using global navigation satellite system (GNSS) control for waypoint navigation of the corner system.
2. Description of the Related Art
Mechanized center-pivot irrigation systems have been used to apply water to large sections of land in an efficient manner to greatly improve crop production. To overcome the limitation of irrigating only a circular pattern, a corner system can be added to the end of a center pivot to irrigate additional areas of a square, rectangular or irregular-shaped field.
Corner systems were first introduced in the 1970s and utilized a guidance system for guiding or steering the corner system along a path. The most popular method for guiding a corner system has been through the use of a buried wire which emits an electromagnetic field that can be detected by sensors on the corner system. See U.S. Pat. No. 3,902,668, Daugherty, et al. Drawbacks to this system include obstacles to burying the typical 9500 feet of wire for instance where rocks are present, difficulty in repairing damage to the buried cable and difficulty in changing the path to be followed.
Global navigation satellite systems (GNSS) have recently been used for corner system guidance, utilizing GPS satellites. U.S. Pat. No. 6,095,439, Segal, et al. disclosed a method for determining optimum steer angle based on the error between a computed pivot-SDU distance and an ideal pivot-SDU distance. U.S. Pat. No. 6,290,151 B1, Barker, et al. also disclosed a method of steering the corner based on the error between the actual rover distance from the pivot point versus an intended distance from the pivot point and additionally a method of projecting a virtual position at a selected length of travel to determine steering. U.S. Pat. No. 6,923,390 B1 Barker, et al. disclosed a method of using two antennas that rotate with steering movement, with the antenna leading in the direction of travel used to determine the distance from a point midway between two selected points on the path of travel. U.S. Pat. No. 8,401,704 B2 Pollock, et al. disclosed a method of using two GNSS antennas to compute a vector orientation to control the corner system, with one antenna located at the hinged connection of the pivot to the corner system (last regular drive unit) and one antenna located on the corner system boom.
In US Patent Application Publication No. 2011/0153161 A1 published Jun. 23, 2011, applicants John Grabow, et al describe a corner guidance control system using two antennas attached by a rail system at a right angle to a corner system wheel, with the two antennas used to calculate current position of the wheel for steering purposes and to calculate a tilt angle from the altitude of the two antennas.
In US Patent Publication No. 2012/0010782 A1 published Jan. 12, 2012) applicant John Grabow describes a corner guidance control system using one antenna that is located along a vertical axis through a center of a wheel of the corner unit to acquire current position of the center of the wheel and a wheel angle sensor used to determine the current heading of the wheel. A point is calculated along the corner travel path that is a radial distance from the current position and a future heading is determined to steer the wheel versus the current heading.
The present invention provides an improved system for corner path following that employs global navigation satellite system (GLASS) sensors which utilizes waypoint navigation.